Year	2020
Authors	Tzeng Yih Lam,Lam TY, Guan BT
Author Type	First Author
Paper Title	Modeling stand basal area growth of Cryptomeria japonica D. Don under different planting densities in Taiwan
Journal Title	Journal of Forest Research
Vol.No	25
Issue.No	3
Page(s)	174-182
Level Type	SCI
Total Pages	8
Date of Publication	2020-06-10
Abstract	Stand basal area (BA) is an important parameter, yet significantly influenced by initial planting density, in describing the developments of plantation forests. The effects of initial density on the growth of sugi (Cryptomeria japonica D. Don), an important plantation tree species in Taiwan, have seldom been studied. The goals of this study are to (1) model sugi stand BA growth under different initial densities, and (2) quantify model forecast accuracy. The data were from a spacing trial established in 1950 at the National Taiwan University Experimental Forest. The initial densities were 2500, 1111, 625, and 400 trees ha-1. Ten measurements were carried out up to stand age 65. Using a mixed-effects modeling approach, we fitted a Gompertz model with the initial density as the covariate to describe stand BA growth trends. Results showed that stand BA was the largest for stands with the highest initial density. The maximum current annual increment of the highest initial density was also the largest and reached earlier in stand development than that of the other spacings. Data up to stand age 60 were needed to yield a forecast accuracy within 6% for BA at stand age 65. This study showed that the fitted Gompertz model could adequately capture the general growth trends in stand BA despite unequal measurement intervals. The results agreed with other spacing trials in other regions and tree species, and the model accuracy was acceptable given the availability of data. The prediction accuracy results underlined the importance of long-term growth monitoring.
Language	English
Reference URL	https://www.tandfonline.com/doi/full/10.1080/13416979.2020.1733171